Physiological and Molecular Mechanisms of Glycyrrhiza uralensis Response to Altica deserticola Herbivory

Abstract Altica deserticola is a major pest of the medicinal plant Glycyrrhiza uralensis, whose leaf-feeding damage reduces licorice yield and quality. Here, we integrated physiological assays, transcriptome and metabolome analyses across 0, 6, 12, and 24 h of A. deserticola feeding to dissect licorice defense responses. Compared with the control (0 h), A. deserticola feeding elevated lipoxygenase activity, promoted accumulation of total flavonoids, condensed tannins and soluble sugars, and induced emission of volatiles including (E)-2-hexanal, (E)-3-hexen-1-ol acetate, and (Z)-calamenene. Differentially expressed genes peaked at 12 h, with enrichment in MAPK signaling, α-linolenic acid metabolism, phenylpropanoid, and flavonoid biosynthesis, alongside strong up-regulation of WRKY, bHLH, MYB, AP2/ERF, and C2H2 transcription-factor families. At 24 h, isoflavonoid biosynthesis and purine metabolism were activated, accompanied by accumulation of rotenone, coumestrol, and daidzein, as well as elevated allantoic acid. This work reveals defensive mechanisms in G. uralensis against herbivory and provides theoretical support for molecular breeding of pest-resistant licorice varieties.